Derivative Instruments and Hedging Activities Interest Spread on Interest Rate Swaps and Caps (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount	$ 25,836,064,000	$ 54,226,205,000	$ 25,836,064,000	$ 54,226,205,000	$ 8,076,933,000	$ 48,445,497,000	$ 55,549,424,000	$ 36,528,169,000
Average Notional Amount	13,932,642,000	54,069,162,000	37,837,985,000	52,960,859,000
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net interest expense (income) on interest rate swaps and caps	800,000	19,200,000	(68,100,000)	65,700,000
Net Long Position [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Average Notional Amount	$ 7,600,000,000	$ 41,200,000,000	$ 32,000,000,000.0	$ 39,800,000,000